The present invention relates to a chemically analyzing apparatus for quantifying a density of a substance dissolved in liquid, and in particular to a chemically analyzing apparatus for analyzing a component such as biological fluid or the like.
Conventionally, as to a reagent supply mechanism in a chemically analyzing device, a reagent pipetting mechanism as disclosed in U. S. Pat. No. 4,451,433, and a dispenser mechanism composed of a syringe pump, a flow selector valve and a reagent discharge nozzle have been used.
The above-mentioned reagent pipetting mechanism having a structure and performing the operation which are explained in detail in the above-mentioned U. S. Patent, requires a relatively long time for three-dimensionally moving a nozzle and washing thereof, and accordingly, it can only carry out a limited number of tests per unit time. However, it is suitable for analyzing several kinds of test items.
Further, the above-mentioned dispenser mechanism has a selector valve which is connected thereto with several oncoming tubes from reagent containers, and which is also connected thereto with outgoing tubes in the same number as that from the reagent containers. In addition, the selector valve is connected thereto with a tube communicated with a syringe pump for controlling the flow of reagents. At first, the reagents are filled in the tubes between the reagent containers and the selector valve and tubes between the selector valve and reagent discharge nozzles. In this initial condition, in order to discharge a desired reagent, the selector valve is operated so as to communicate a tube from the corresponding reagent container with the syringe pump which effects suction so as to draw up a predetermined volume of the desired reagent into the tube on the syringe pump side through the selector valve. Then, the selector valve is again operated so as to connect the tube between the syringe pump and the selector valve with a tube between the selector valve and associated one of the reagent discharge nozzles. In this condition, the syringe pump discharges the reagent by a predetermined quantity into a reaction container from the tube. Accordingly, this mechanism can perform the change-over and supply of reagents at a high rate. However, this mechanism is not suitable for being used in such a case that several kinds of reagents are used since the reagent discharge nozzles should be provided by a number equal to the number of kinds of reagents to be used. Rather, this mechanism is suitable for test item such that the number of kinds of reagent is small, but the number of tests is large.
Conventionally, an automatic analyzing apparatus having a piston mechanism is disclosed in Japanese Laid-Open Patent No. S63-131066. This apparatus is at first aim at decreasing the size thereof by overlapping the moving locus of a holder for holding a reagent container with that of a holder for holding a reaction container. A reagent is discharged by a piston integrally incorporated with a side wall of the associated one of the reagent containers. The piston is driven by a piston rod drive device provided at a discharge position of the reagent. At this discharge position, the piston rod drive device associated with this reagent container is transitorily connected to the piston. Then, the piston is lifted up by the piston rod drive device so as to suck the reagent into the piston from the reagent container. When the piston comes up to the uppermost position, the piston is meshed with a gear for rotating the piston, and accordingly, the piston is turned by an angle of 180 deg. by this gear. In this phase, a hole which has been opened for sucking the reagent is closed through the rotation of the piston while a hole communicated with a discharge port is opened. When the piston is moved down, the reagent is discharged into the reaction container from the piston through the hole as mentioned above.
The conventional above-mentioned reagent supply mechanism has offered the following disadvantages.
First, the reagent is uselessly consumed by a certain quantity. That is, in order to prevent the reagent sucked in a nozzle from being mixed with pure water, an air layer is defined between the reagent and the pure water. However, the water would go along the inner wall of the nozzle and be inevitably mixed with the reagent in the upper part of the latter. Accordingly, in order to prevent the reagent mixed with the water from being used for analysis, the reagent is sucked into the nozzle by a quantity which is greater than a quantity actually required for analysis by about 30%. The reagent to be used for the analysis is very expensive, and accordingly, such an extra quantity of the reagent causes the inspection cost to uselessly increase.
Second, it requires a long time and a much volume of liquid for washing. That is, in order to prevent reagents from being mixed with one another through the nozzles, the interior and the exterior of the nozzle are washed every time with washing liquid, and accordingly, a larger volume of the washing liquid and a longer washing time are required.
Third, residue is more or less left even though the interior and the exterior of the nozzle are washed by the washing liquid, and accordingly, errors in measured values are inevitably caused.
In the case of a reagent dispenser mechanism, the following two disadvantages are caused:
First, the reagent is uselessly consumed similar to that mentioned above. In order to rapidly discharge any one of reagents, all reagents are previously filled in tubes connecting the reagent containers to a selector valve and tubes connecting the selector valve to discharge ports. The reagents charged in these tubes are uselessly discarded when the apparatus is stopped. In some cases, the reagent is discarded by a quantity corresponding to that for more than 100 persons although it depends upon kinds of the reagents, and the lengths of the tubes.
Second, the maintenance for the selector valves is troublesome. That is, various kinds of the reagents pass through the selector valve one by one, and accordingly, the selector valve becomes gradually contaminated. In some cases, a valve element would stick to a valve seat since various kinds of reagents make contact with each other. Thus, it is required to periodically disassemble and wash the selector valve.
In the case of a piston type as a third example, the reagent is consumed by a less quantity in comparison with any of the above-mentioned examples. However, since the reagent still remains in a passage extending from a reagent container to a tip end of a pipetter even after the apparatus is shut down, and accordingly, the reagent in that part is uselessly discarded. Further, although the quantity of the reagent to be fed has to be changed, depending upon a density of a sample, it is impossible to discharge the reagent by a volume other than that previously set due to a fixed distance of reciprocation of the piston since the position of a gear provided in the upper part of the piston, for rotating the same, is fixed. Further, since the piston is provided to one side surface of the associated container, it is required to pump up the reagent up to a position which is higher than the position of the reagent container. Further, a pressure loss through the passage extending from the reagent container to the tip end of the pipetter is not negligible. Accordingly, a pressure should be applied more or less, and accordingly, the drive mechanism for the piston becomes complicated and large-sized. That is, the use of a simple and small-sized pump has been hindered.
As mentioned above, any one of conventional reagent supply systems offers a problem of consumption of useless reagents. Further, the reagent pipetting mechanisms requires a large quantity of washing liquid in order to prevent contamination between reagents. Further, the reagent dispensing mechanism requires troublesome disassembly and washing. Further, the piston system cannot supply a reagent only by a predetermined quantity. Alternatively, it has a complicated structure.
Further, Japanese published PCT Application (Published Japanese Translation of PCT application) No. H6-510582 discloses an example of conventional micropumps for discharging a slight quantity of reagent or the like. This micropump is a static-electrically driven diaphragm micropump which includes a first pump body having conductive electrode zones electrically connected to a voltage source and electrically insulated from one another, a second pump body provided therein with a diaphragm area, and a pump chamber incorporating a flowing direction control means having a resistance depending upon a flowing direction of drawn-up fluid, and in which two pump bodies define therebetween a hollow space making contact with the diaphragm area and filled therein with fluid medium spatially separated from fluid drawn up, and the conductive electrode zones of the pump body are arranged so that the fluid medium is subjected to electric fields produced between the above-mentioned conductive electrode zones while the drawn-up fluid is hardly subjected to the electric fields. In this conventional structure, the diaphragm is deformed by static electricity for drawing up liquid, and then, the static electricity is removed so that the diaphragm exhibits its restoring force with which the liquid is discharged.
However, the conventional static-electrically driven micropump as mentioned above, is the one for discharging liquid into liquid. However, this device has offered a problem such that the characteristic of liquid discharge into gas in the case of an inkjet printer or a biochemical automatic analyzing device in which a reagent is discharged, or the like, is inferior, and accordingly, which has not yet been practically developed. Thus, inkjet printers of a piezoelectric disc type, evaporating type or the like, which are expensive have been prosperously used, and further, biochemically analyzing devices of the piezoelectric type or the like have hardly been used since their costs are high and their reliability is low.
The above-mentioned problems of the static-electrically driven discharge micropump are caused by such a fact that liquid is sucked up through the electrostatic deformation of the diaphragm, and is discharged by the restoring force of the diaphragm which is effected for allowing the diaphragm to take its original shape when the static electricity is removed. Accordingly, the diaphragm is designed to have a high degree of rigidity. However, when the diaphragm is deformed through the application of the static electricity so as to store a force, the discharge pressure becomes soon lower as the degree of deformation of the diaphragm becomes small even though the discharge pressure is high upon initiation of the discharge. Thus, the static electricity can not be used satisfactorily, that is, the efficiency is low. For example, in the case of the application of this pump for discharging a reagent in a biochemically analyzing apparatus in which liquid is discharged into gas, or the like, the stream of the reagent has less momentum so that the sensitive operation of a discharge nozzle part cannot be expected, and accordingly, residual liquid drops are present in the discharge nozzle part, thereby satisfactory discharge with a high degree of reproducibility can hardly be expected.
Accordingly, one object of the present invention is to provide a chemically analyzing apparatus incorporating a simple reagent supply mechanism (discharge device) which can prevent reagents from being uselessly consumed, and which does not require a substantial quantity of washing liquid and periodic disassembly and washing, and with which the quantity of a reagent can be simply changed.
To the end, according to the present invention, there is provided a chemically analyzing apparatus comprising a reacting container holder with which a sample and a reagent are fed at a predetermined position, for holding a plurality of reacting containers, a measuring device for measuring physical properties of the sample, a plurality of reagent containers having lower parts, and liquid feed means provided respectively in the lower parts of the reagent containers, being associated with the latter.
It is noted that each liquid feed means is provided therein with a pressing pin as a drive device for a diaphragm in a liquid feed chamber, and the pressing pin is driven at a predetermined speed in a direction substantially orthogonal to the diaphragm so as to press the diaphragm in the direction in which the volume of the liquid feed chamber is decreased in order to discharge the fluid from the liquid feed chamber.